Omni-directional antenna system



y 1959 R. LA ROSA 2,885,678

OMNIDIRECTIONAL ANTENNA SYSTEM I Filed July 30, 1954 Ll? HYBRID TRANSMITTER JUNCTION RECEIVER so" PHASE- SHIFT LINE SECTION .FIGZ FIG.3

United States Patent OMNI-DIRECTIONAL ANTENNA SYSTEM Richard La Rosa, Levittown, N.Y., assignor to Hazeltiue Research, Inc., Chicago, Ill., a corporation of Illinois Application July 30, 1954, Serial No. 446,939 7 Claims. (Cl. 343-852) This invention relates to antenna systems and, in particular, to omnidirectional duplex antenna systems of the type suited for microwave applications.

In transmitter-receiver systems utilizing the same antenna system for radiating :and intercepting signals, it is necessary to provide a duplexer capable of coupling the transmitter to the antenna system while isolating the receiver from the transmitter to prevent damaging the .receiver during the transmission of signals. The duplexe-r must also be capable of coupling the receiver to the antenna system during the interception of signals. One prior duplex antenna system satisfactorily protects the receiver during the transmission of signals by the transmitter and couples the receiver to the antenna system during the interception of signals but has the disadvantage that a substantial portion of the signal power generated by the transmitter is dissipated uselessly in a dummy load included in the system for impedance matching or balancing purposes. Another type of duplex antenna system previously proposed has the disadvantage that it does not provide an omnidirectional antenna characteristic which is desirable for many applications.

It is an object of the present invention, therefore, to provide a new and improved omnidirectional antenna system in which substantially all the power generated by a transmitter is radiated 'by the antenna system.

It is another object of the invention to provide a new and improved duplex antenna system having an over-all omnidirectional antenna characteristic.

It is another object of the invention toprovide a new and improved duplex antenna .system having an over-all omnidirectional antenna characteristic of uniform intensity.

-In accordance with a particular form of the invention, an omnidirectional antenna system comprises four-terminal hybrid coupling means and first signal-translating means coupled to a first terminal of said hybrid means. The antenna system also includes second signal-translating means coupled to a second terminal of said hybrid means isolated from said first terminal and a pair of antennas individually having predetermined cardioid-shaped directional characteristics space-displaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for translating energy'with respect to the first and second signal-translating means. The hybrid means provides a predetermined phase shift of signals translated between one of the antennas and the first and second signal-translating means with respect to signals translated between the other antenna and the first and second signal-translating means to provide an over-all omnidirectional antenna characteristic.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing:

Fig. l is a schematic diagram of a duplex antenna sys-'-' tem constructed in accordance with the invention coupled to a transmitter and receiver;

Fig. 2 is a diagram representing the directional characteristics of the antennas of the Fig. 1 system;

Fig. 3 is a diagram representing the overall antenna characteristic of the antenna system, and

Fig. 4 is a vector diagram representing phase relations of signals intercepted by the antenna system.

Referring now more particularly to Fig. 1 of the draw ing, the duplex antenna system there represented com prises four-terminal hybrid coupling means including 'a' hybrid junction 11 of a conventional type, for example, of the so-called Magic T type described at pages 350- 352, inclusive, of the text, Microwave Duplexers (Massachusetts Institute of Technology) Radiation Laboratory Series, volume 14, edited by Smullin and Montgomery, McGraw-Hill, 1948. The hybrid coupling means also includes transmission line or wave guide sections 12,

13, 14, and 15 having lengths, more fully described .hereinafter.

.First signal-translating means or signal-transmitting means comprising the output circuit of a microwave trans-.

mitter 16 is coupled to a terminal 10 of the transmission line 12 coupled to a first branch of the hybrid junction 11. Second signal-translating means or signal-receiving means comprising the output circuit of a receiver 17 is coupled to a terminal 20 of the transmission line "13: coupled to a second branch of the hybrid junction 11.

Because of the inherent signal-translating characteristics of the hybrid junction, the terminal 20 is effectively isolated from the terminal 10, as will be more apparent subsequently.

There is also provided a pair of antennas 18, 19 individually having predetermined directional characteristics and individually coupled to third and fourth terminals 30, 40, respectively, of the hybrid means for radiating transmitted energy and for intercepting energy for ap The hybrid means comprising the junction 11 and .asso" ciated transmission lines 1215 provides a predetermined. phase shift of signals translated between the antenna 18 and the transmitting and receiving means 16, 1'7 with respect to signals translated between the other antenna 19 and the transmitting and receiving means to provide an over-all omnidirectional characteristic. To this end, the transmission line 14 preferably includes :a

quadrature or phase-shift transmission line secti'on,. not included in the transmission line 15, for providing :a

quadrature-phase shift of signals translated between the antenna 18 and the transmitter 16 and receiver 17 with respect to signals translated between the antenna 19 and the transmitter and receiver toprovide an over-all omnidirectional antenna characteristic of uniform intensity. In other words, the transmission line 14 preferably is. longer than the transmission line 15 by one-quarter of the wavelength of the transmitted signals.

Considering now the operation of the Fig. 1 system,"-

with the impedances of the four branches of the hybrid junction 11 properly matched by the impedances of the antennas 18, 19 and the transmitter 16 and the receiver 17, signals generated by the transmitter flow to the hybrid junction 11 where an equalpowe'r division of the signals 1 Patented May 5, 1959 between transmission lines 14 and 15 occurs to provide signal flow from the transmitter 16 to the antennas 18, 19 in the manner indicated by solid-line arrows 50. None of the signals developed by the transmitter 16 flows to the receiver 17 because of theinherentsignaltranslating characteristics of the hybrid junction 11. The signals applied to the transmission lines 14, 15 by the hybrid junction 11 are initially of the same phase but during translation of the signal by the transmission lines 14, 15 to the antennas 18, 19, respecti ely, the 90 phase-shift line section 14a causes the signals applied to the antenna 18 to lag the signals applied to the antenna 19 by 90.

As previously mentioned, the antennas 18, 19 preferably have directional characteristics represented by Curves A and B of Fig. 2 which may be expressed mathematically by Equations 1 and 2, respectively.

A=cos% B=cos g where The field intensity of the signal radiated by the antenna 18 at a given distant point in the direction may, for example, have an amplitude represented by arrow 0 while the field intensity of the signal radiated by the antenna 19 has the intensity represented by the arrow d. Since the signal radiated by the antenna 18 lags the signal radiated by the antenna 19 by 90 in time phase, the signal intensities at the given distant point may be represented vectorially by arrows c and d of Fig. 3 providing a resultant signal intensity represented by arrow c. It may readily be demonstrated that the field intensity at any point of the same distance from the antennas 18, 19 as the given distant point has an amplitude represented by the arrow 2, providing an overall omnidirectional antenna characteristic of uniform intensity represented by curve G. This may be expressed by the following equations:

where =resultant field intensity of signals radiated by antennas 18, 19 at a distant point in the direction 6.

When the antenna system intercepts signals radiated from a distant point, the antenna 18 translates the intercepted signals along transmission line 14 to the hybrid junction 11 where they divide with equal power and are supplied to the transmitter 16 and receiver 17 in a manner indicated by dashed-line arrows 60. Similarly, signals intercepted by the antenna 19 are translated by the transmission line 15 to the hybrid junction 11 where they divide with equal power and are applied to the transmitter 16 and receiver 17 in the manner indicated by dotted-line arrows 70. This division of intercepted. signal energy by hybrid junction is accomplished because of the inherent signal-translating characteristics of the junction. The signals intercepted by the antennas 18, 19 have the same phase at the antennas but the signal translated by the transmission line 14 lags the signal translated by the transmission line 15 at its point of application to the junction 11 because of the 90 phase shift accomplished by the line section 14a. At the junction 11, therefore, there is provided a vectorial dashed-line arrow 61 and dotted-linearrow 71 of Fig. 4

signal relation indicated by which represents signals intercepted by antennas 18, 19, respectively, as they are applied to the junction 11. The signal represented by arrow 71 is translated through the junction 11 without phase shift while the signal represented by arrow 61 is translated with a phase reversal through the junction to develop at th transmission line 13 signals represented by arrows 62 and 71 of Fig. 4. These signals have a resultant amplitude represented by arrow 80.

As the direction of the intercepted signal shifts causing the relative amplitudes of the signal intercepted by the antennas 18, 19 to vary in accordance with the cardioid directional receiving characteristics thereof, the sum of the squares of the signal amplitudes and thus the resultant signal amplitude developed at the transmission line 13 remains constant, thereby providing the antenna system with an effective omnidirectional receiving characteristic of uniform intensity represented by curve F of Fig. 4.

It will also be understood that during the generation of signals by the transmitter 16 because of the close proximity of antennas 18, 19, any signals radiated by, for example, the antenna 18 and intercepted by the antenna 19 have their counterpart in signals radiated by the antenna 19 and intercepted by the antenna 18. Because of the symmetrical nature of the transmitting system, these intercepted signals have the same total phase delay upon their application to the hybrid junction from the intercepting antenna. Thus, because of the inherent signal-translating characteristic of the junction 11, these intercepted signals cancel one another at the transmission line 13 and thus do not disturb the receiver 17. Further, because of the signal separation accomplished by the duplex antenna system, the system may be utilized simultaneously to transmit and to receive signals from a distant point.

From the foregoing description it will be apparent that a duplex antenna system constructed in accordance with the invention has the advantages of providing an omnidirectional transmitting-receiving characteristic of uniform intensity while gainfully utilizing the total signal power developed by the transmitter coupled to the system.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What isclaimed is:

1. A duplex antenna system for microwave signals comprising: four-terminal hybrid microwave coupling means; microwave signal-transmitting means coupled to a first terminal of said hybrid means; microwave signalreceiving means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas having like cardioid-shaped directional characteristics space-displaced by and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for radiating transmitted energy and for intercepting energy for application to said receiving means; said hybrid coupling means comprising a microwave hybrid junction and microwave transmission lines coupled between the terminals of the junction and said antennas and receiving and transmitting means and including a quadrature-phase shift transmission-line section coupled between one of the junction terminals and one of the antennas for providing a quadrature-phase shift of signals transated between said one antenna and said transmitting and receiving means with respect to signals trans ated between the other antenna and said transmitting and receiving means to provide an over-all omnidirectional antenna characteristic of uniform intensity.

2. A duplex antenna system comprising: four-terminal hybrid coupling means; signal-transmitting means coupled to a first terminal of said hybrid means; signal-receiving means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas individually having predetermined cardioid-shaped directional characteristics space-displaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for radiating transmitted energy and for intercepting energy for application to said receiving means; said hybrid means providing a predetermined phase shift of signals translated between one of said antennas and said transmitting and receiving means with respect to signals translated between the other antenna and said transmitting and receiving means to provide an over-all omnidirectional antenna characteristic.

3. A duplex antenna system comprising: four-terminal hybrid coupling means; signal-transmitting means coupled to a first terminal of said hybrid means; signal-receiving means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas individually having like cardioid-shaped directional characteristics space-displaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for radiating transmitted energy and for intercepting energy for application to said receiving means; said hybrid means comprising a hybrid junction and phase-shifting means coupled between one of the junction terminals and one of said antennas for providing a predetermined phase shift of signals translated between said one antenna and said transmitting and receiving means with respect to signals translated between the other antenna and said transmitting and receiving means to provide an over-all omnidirectional antenna characteristic.

4. A duplex antenna system comprising: four-terminal hybrid coupling means; signal-transmitting means coupled to a first terminal of said hybrid means; signal-receiving means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas having like cardioid-shaped directional characteristics space-displaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for radiating transmitted energy and for intercepting energy for application to said receiving means; said hybrid means providing a predetermined phase shift of signals translated between one of said antennas and said transmitting and receiving means with respect to signals translated between the other antenna and said transmitting and receiving means to provide an over-all omnidirectional antenna characteristic of uniform intensity.

5. A duplex antenna system comprising: four-terminal hybrid coupling means; signal-transmitting means coupled to a first terminal of said hybrid means; signal-receiving means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas having like cardioid-shaped directional characteristics space-displaced by and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for radiating transmitted energy and for intercepting energy for application to said receiving means; said hybrid means providing a quadrature-phase shift of signals translated between one of said antennas and said transmitting and receiving means with respect to signals translated between the other antenna and said transmitting and receiving means to provide an over-all omnidirectional antenna characteristic of uniform intensity.

6. An omnidirectional antenna system comprising: four-terminal hybrid coupling means; first signal-translating means coupled to a first terminal of said hybrid means; second signal-translating means coupled to a second terminal of said hybrid means isolated from said first terminal; and a pair of antennas individually having predetermined cardioid-shaped directional characteristics spacedisplaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for translating energy with respect to said first and second signal-translating means; said hybrid means providing a predetermined phase shift of signals translated between one of said antennas and said first and second signal-translating means with respect to signals translated between the other antenna and said first and second signal-translating means to provide an over-all omnidirectional antenna characteristic.

7. An omnidirectional antenna system comprising: four-terminal hybrid coupling means; first signal-translating means coupled to a first terminal of said hybrid means; second signal-translating means coupled to a sec ond terminal of said hybrid means isolated from said first terminal; and a pair of antennas having like cardioidshaped directional characteristics space-displaced by 180 and having a common phase origin in space and individually coupled to third and fourth terminals of said hybrid means for translating energy with respect to said first and second signal-translating means; said hybrid means providing a quadrature-phase shift of signals translated between one of said antennas and said first and second signal-translating means with respect to signals translated between the other antenna and said first and second signal-translating means to provide an over-all omnidirectional antenna characteristic of uniform intensity.

References Cited in the file of this patent UNITED STATES PATENTS 

